The present invention broadly relates to fire alarm equipment or systems and, more particularly, pertains to a new and improved construction of an alarm system in which smoke detecting light beams of extinction-type smoke detectors having spatially separate light transmitters and receivers are utilized as paths or carriers for signal transmission.
Generally speaking, the method of the present invention employs individual extinction-type smoke detectors for detecting smoke on the principle of attenuation of a light beam extending between a light transmitter and separate light receiver in the presence of smoke. In other words, the method of the present invention is for operating a fire alarm system and comprises the steps of employing at least two extinction-type smoke detectors each having a light transmitter and a light receiver separate from the light transmitter for detecting smoke by measuring the attenuation in the presence of smoke of a light beam transmitted from the light transmitter to the separate light receiver and generating an information-bearing signal in response to a physical parameter detected and evaluated by electronic circuitry.
An alternate method of the present invention for operating a fire alarm system comprises the steps of employing at least two extinction-type smoke detectors each having a light transmitter and a light receiver separate from the light transmitter for detecting smoke by measuring the attenuation in the presence of smoke of a light beam transmitted from the light transmitter to the separate light receiver, generating a fire alarm signal in at least one of the separate light receivers in response to a detection of smoke and conducting the fire alarm signal to the light transmitter of a subsequently arranged smoke detector of the extinction-type smoke detectors.
The first alarm system of the present invention employs at least two extinction-type smoke detectors for detecting smoke by the attenuation of at least one light beam in the presence of smoke and comprises a light receiver for each of the at least two extinction-type smoke detectors and a light transmitter arranged separate and remote from the light receiver for each of the at least two extinction-type smoke detectors for transmitting a light beam to the light receiver.
In hitherto known fire alarm systems, a desired number of fire or smoke detectors of thermal, ionization, light-scattering, extinction or radiation types have been installed according to requirements at locations in buildings, factories, underground markets, tunnels, hangars, warehouses and similar structures and interconnection among these fire or smoke detectors as well as their connection to a receiver unit or central station are realized by using conductors which serve for both power supply and signal transmission, as is disclosed, for example, in Japanese Utility Model Publication No. 39518/1980. Accordingly, the total length of the signal conductors utilized is enormous, involving extremely high expenditures for the wiring.
The same disadvantage also applies to the wiring for signalling equipment other than fire alarm systems such as, for example, failure alarm signal transmission for machine tools, transmission of information in burglar alram systems and similar systems. Furthermore, such signal lines are prone to pick up electric noise or interference generated by various instruments or devices, possibly causing erroneous operation such as the generation of a false fire alarm signal or false failure alarm signal.